Controller for 401

Onvinyl · 27th December 2006, 10:55 AM

Hi,
another long-term project is a controller for my Garrard 401.

It will consist of a sine-wave generator at 50Hz and a power amp.
Since now, I only saw circuits that use an output transformator to achieve the desired 220 V.
I don't feel too comfortable with this, as I think that the lower the THD the better, and that is not where OPTs excell at low frequencies.
Do you know of any amps around 15Watts and around 200V output? I don't care wheter if it's a chip amp, mosfet or tubes.
Rüdiger

Mark Kelly · 27th December 2006, 11:07 AM

I have measured -80dB distortion on my regenerated power supplies for turntables using a toroidal step-up transformer. The ugly magnetics of the Garrard motor will cause much higher levels than this.

The trick is to use a somewhat over-rated transformer so that the flux in the core is kept within linear bounds.

pinkmouse · 27th December 2006, 11:12 AM

Hi Rüdiger

I may be missing the point here, but why are you worrying about THD in a traffo? Firstly, the average mains traffo is designed to be used at this frequency, so it might be worth firing up RMAA and seeing if there actually is a problem that needs to be fixed. The other issue is the actual effect it will have. Whilst THD will affect the movement of a cone measuring a couple of grammes, with the Thorens you are driving a mechanical system massing kilos, I would expect that any THD would be damped out of existence.

edit: Wrote this reply whilst Mark posted, so I accept that distortion may be measurable, but still am not convinced that it will affect the overall result that much.

Onvinyl · 27th December 2006, 11:30 AM

Hi Al, hi Mark,
I admit that using a bigger transformer will most probably solve most if not all my issues.
OTOH, not to use an additional trafo may reduce cost and effort.

And yes, several people reported, that the key features of a motor controller for a TT are lowest distortion and most stable frequency. So to judge the outcome of an additional controller it shall have those features.
Rüdiger

pinkmouse · 27th December 2006, 12:38 PM

Mark, did you break that distortion down? Just wondering how much is due to just the traffo, and how much for the rest of the circuit.

27th December 2006, 10:55 AM	#1
Onvinyl diyAudio Member Join Date: Aug 2002 Location: Germany	Controller for 401 Hi, another long-term project is a controller for my Garrard 401. It will consist of a sine-wave generator at 50Hz and a power amp. Since now, I only saw circuits that use an output transformator to achieve the desired 220 V. I don't feel too comfortable with this, as I think that the lower the THD the better, and that is not where OPTs excell at low frequencies. Do you know of any amps around 15Watts and around 200V output? I don't care wheter if it's a chip amp, mosfet or tubes. Rüdiger __________________ "I can feel what's going on inside a piece of electronic equipment. I have a sense that I know what's going on inside the transistors." Robert Moog

27th December 2006, 11:12 AM	#3
pinkmouse diyAudio Moderator Join Date: Apr 2002 Location: Chatham, England	Hi Rüdiger I may be missing the point here, but why are you worrying about THD in a traffo? Firstly, the average mains traffo is designed to be used at this frequency, so it might be worth firing up RMAA and seeing if there actually is a problem that needs to be fixed. The other issue is the actual effect it will have. Whilst THD will affect the movement of a cone measuring a couple of grammes, with the Thorens you are driving a mechanical system massing kilos, I would expect that any THD would be damped out of existence. edit: Wrote this reply whilst Mark posted, so I accept that distortion may be measurable, but still am not convinced that it will affect the overall result that much. __________________ Al I conceive of nothing, in religion, science or philosophy, that is more than the proper thing to wear, for a while. Charles Fort

27th December 2006, 11:30 AM	#4
Onvinyl diyAudio Member Join Date: Aug 2002 Location: Germany	Hi Al, hi Mark, I admit that using a bigger transformer will most probably solve most if not all my issues. OTOH, not to use an additional trafo may reduce cost and effort. And yes, several people reported, that the key features of a motor controller for a TT are lowest distortion and most stable frequency. So to judge the outcome of an additional controller it shall have those features. Rüdiger __________________ "I can feel what's going on inside a piece of electronic equipment. I have a sense that I know what's going on inside the transistors." Robert Moog

27th December 2006, 12:38 PM	#5
pinkmouse diyAudio Moderator Join Date: Apr 2002 Location: Chatham, England	Mark, did you break that distortion down? Just wondering how much is due to just the traffo, and how much for the rest of the circuit. __________________ Al I conceive of nothing, in religion, science or philosophy, that is more than the proper thing to wear, for a while. Charles Fort

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

27th December 2006, 11:07 AM	#2
Mark Kelly diyAudio Member Join Date: Feb 2006 Location: Geelong	I have measured -80dB distortion on my regenerated power supplies for turntables using a toroidal step-up transformer. The ugly magnetics of the Garrard motor will cause much higher levels than this. The trick is to use a somewhat over-rated transformer so that the flux in the core is kept within linear bounds.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Samsung 1602VFD For CDROM Controller & Remote Volume Controller	slowgay	Swap Meet	2	22nd November 2008 02:44 PM
USB controller	muky006	Digital Line Level	1	15th October 2008 04:53 AM
DIY dac ver.3 and cd-rom controller kit	Kip	Digital Source	57	4th September 2006 09:24 PM
I2C Controller	abid_rehan	Digital Source	1	21st October 2004 10:02 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read